Molding of pipes and like hollow articles



Patented Mar. I927. v, UNITED STATES PATENT OFFICE.-

MARCEL LEVY, OF GENEVA, SWITZERLAND, ASS IGNOR T0 PRODOR FAIBRIQUE DE PRODUITS ORGANIQUES S. A., 0F CANTON OF GENEVA, SWITZERLAND, A CORPORA- TION.

MOLDING.OE PIPES AND LIKE .HOLLOW ARTICLES.

N0 Drawing. Original application fil ed November 2, 1922, Serial No. 598,651, and in Switzerland November 16, 1921. Divided and this application filed July 22, 1924. Serial No. 727,575.

This inventionrelates to the molding of pipes and like hollow or solid articles from concretes prepared by heat from a graded filler and a hard binding agent. the latter of which may either be hard pitch. as referred to in my co-pending application No. 598,651 filed on 2nd November, 1922, or sulphur.

When it is desired to apply such concretes to the construction of large hollow bodies, especially such as pipes or conduits, difficultiesarise in preventing cracking of the pipes or the like on cooling of the mixture after or during setting.

The present invention consists in a process comprising withdrawing the casting from the mold or removing the mold from I the casting while, the concrete is still hot or warm. It is desired to emphasize the fact that the forms are separated from the finished pipe as quickly as possible, namely as soon as the pipes are capable of being ban: dled without deformation, not for the purpose of making these forms available for refilling because this is quite unimportant, but for the urpose of ensuring that the molded artic es shall cool Without cracking. Applicant has made an important dis covery on which the present invention is based, namely that by hot stripping of the forms or shells in practical working a very high percentage of the cast objects cool without cracks, whereas if stripping-is effected in the ordinary way the percentage is low. According to one form of the invention shells or molds are so constructed that they can be removed as soon as the concrete is hard but while it is still hot.

Instead of removing the shells immediate- 1y after the concrete has set, these .are so constructed that so soon as the concrete has set certain parts of the shells or molds can be removed in order to enable the concrete to contract freely.

The concrete may be cooled by means of air or cold water, which however requires certain precautions, for instance the concrete as soon as it has been cast into molds must be uniformly cooled and cooling must be continued until the concrete has set. The removal of the shells or molds must always 'be eifected while the concrete is still hot, or it is necessary as mentioned above to take care that the shells are so constructed-that when the wedges are removed, the shell allows the concrete to contract.

If sudden cooling is efl'ected it is advisable to exert a small pressure through the filling aperture in order to prevent the formation of holes or blisters in' consequence of too rapid cooling.

The improved concrete used 'in the presv ent invention must not be confused with the mixtures containing tar which are used for coating roads and thedike because these mixtures must be more or-less soft, plastic and resilient and are not suitable for construction of high pressure pipes for pres- These .facts assist in bringing out the.

feature of the present invention still more because mixtures prepared with asphalts which are not hardened are not sufficiently strong but are plastic and cannot be. used in the'manufacture of pipes; for this reason it is necessary to reinforce such pipes with wood, cement concrete. glass or pulp. The only kinds of pitch which at present 'are able to be sold are pitches. which are not extremely hard. For this reason pitch which is produced as ahard pitch before it is placed on the market is softened by the addition of oils. The pitch which is required for the present invention as opposed to this softened pitch must be extremely hard.

According to the new process it is possible to obtain pipes without the necessity of strengthening them which are stronger than cement pipes and this even at the highest temperatures reached when exposed to the rays of the sun.

Hereinafter there is given an example of a pipe which has been produced by means of gas tar, the distillation of which has been carried through to a sufficient extent in order to obtain .a pitch which is' very hard and remains hard at temperatures of 80 C. and over. With this very hard pitch, which is very brittle and shin there is obtained when it is melted and mixed with broken stone, sand 'and stone powder a concrete which when cast into pipe molds 30 cm. in diameter, ,4

cm. thick and 1 meter long, pipes are formed which was cast .in the same mold as that which was used for the new concrete, i. e. which had exactly the same dimensions and subjected to pressure under the same conditions, only 2,500 kgs. were necessary to produce the a fracture.

' pipes of the new concrete are stronger, more resistant against chemical action and at the same time are impermeable to water and possess very smooth surfaces;

For small objects which are simple in shape a concrete can be used without gravel or large'pieces especially when care is taken that the concrete is cooled from the outside, while its interior is kept comparatively warm.

The presence of coarse gravel,,or better of broken stone, plays a very important part in the preparation of the new concrete.

I Sulphur may be used as a binding agent in place of the specially hard pitch,

As a general rule it is possible to say that:

The more compact the structure of the solid body the smaller will be the quantity of binder required:

'(z'i) The greater the proportion of the solid body in the filling material the smaller will be the liability of the concrete to crack;

In order to obtain quite smooth surfaces which are even smoother than those of glazed earthenware goods and which is of great importance in the .case of pipes, the new concrete is poured into previously heated molds or shells provided with smooth surfaces. In the case of wooden shells'or .molds polished wood may be employed orbetter still wood covered with sheet ironor the like. I

Having now described my invention what I claim as new and desire to secureby Letters Patent is e y 1. The method of molding hollow concrete articles from hot concretes which comprises casting them in molds with cores, removing any parts of -said molds and cores which impede the contraction of the concrete on cooling after the concrete has set, thereby allowing the free contraction of said concrete.

2. The method of molding hollow concrete articles from hot concretes which comprises casting them in molds with cores, removing any parts of said molds'and cores which impede the contraction of the'concrete on cool-. ing after the concrete. has and while said concrete is still hot.

3. The method of molding hollow concrete articles from hot concretes which comprises casting them in molds with cores, removing any parts of said molds and cores which impede the contraction of the concrete on cooling, after the concrete has set and while said concrete is still hot, thereby allowing the =free contraction of said concrete.

4. The method of molding smooth hollow concrete articles from hot pitch concretes which comprises casting them in smooth previously-heated molds with cores, .removing any parts of said molds and cores which impede the. contraction ofthe concrete on cooling after the concrete has set and'while the concrete is still hot, thereby allowing the free contraction of said concrete.

MARCEL LEVY. 

